The interrupted field time-of-flight transient photoconductivity technique for studying charge transport and trapping in high resistivity semiconductors†

Abstract

In conventional time-of-flight (TOF) transient photoconductivily experiments, a high resistivity semiconductor device is biased and thin sheet of charge carriers is photoinjected at one end of the sample by a short duration light pulse. The drift of the injected charge sheet across the device under the action of the internal field gives rise to a photocurrent which is readily measured in the external circuit. The interrupted field TOF (IFTOF) technique is a powerful tool for studying the interaction of the photoinjected carriers with traps and recombination centres in the material by momentarily stopping the charge sheet anywhere in the sample. Although the IFTOF technique has a number of distinct advantages for studying charge trapping and release processes in high resistivity solids, it has generally not been adopted as a convenient experiment since the sample capacitance results in large displacement currents at switching. An experimental apparatus is described that eliminates displacement current effe...